And I strongly disagree with you on the value of lvalue subroutines.
As you indicate, you're throwing away the possibility of value validation. Whether or not you currently do any value validation, it is important to me to have the option. (If for no other reason than the fact that you can retroactively add it to help track down bugs.) Furthermore I take objection to being told that my programming practice is flawed because of a disagreement like this.
Saying that you can use attributes to get value validation back doesn't comfort me. As I've repeatedly noted, I avoid attributes because the CHECK method may not be run for modules in my environment. So offering a buggy solution to replace a non-solution doesn't comfort me.
I really like Ruby's compromise. You have the methods bar and bar= that can do anything they like. If they do what the names suggest then foo.bar acts like an lvalue. The language has a syntax that makes autogenerating (very effient and barebones) versions of these trivial. But you can do whatever you want.
However in Perl I'll continue to use rvalue accessors, thankyouverymuch.